FREDERICTON - A recent heavy-water spill at New Brunswick's Point Lepreau nuclear power plant could have been avoided if changes had been made after similar incidents almost 17 years ago, a new report says.

The NB Power report, obtained by The Canadian Press, says heavy water entered a gas monitor three times during a shutdown in 1995, but the design was never changed.

It states that documentation wasn't updated to require a particular valve to be closed.

"A contributing factor was that the previous similar occurrences in 1995 ... did not result in actions to address this issue," the report says.

"Those events created a potential opportunity to either analyse and correct the design deficiency, or to record the rationale and revise the ... documentation."

The power plant was evacuated in mid-December after four to six litres of heavy water spilled from a piece of monitoring equipment known as a gas chromatograph.

At the time, the plant's heavy-water system was being refilled as part of the utility's plan to restart the generating station after it is refurbished.

The Crown-owned utility said there were no health concerns for workers or the public during the spill.

Plant spokeswoman Kathleen Duguay said Wednesday that the 1995 incidents were documented, but not in all the places where it was needed.

"We have a better system today," Duguay said. "We have a rigorous system to track this ... That piece of equipment has been repaired, and the moderator system has been filled."

Duguay said the documentation and drawings at Point Lepreau have also been updated.

She said emergency procedures were in place to handle a heavy water leak, and those procedures worked well.

But a long-time critic of Point Lepreau said the incident raises questions about the effectiveness of the federal regulator.

David Coon, policy director of the Conservation Council of New Brunswick, said the regulator should have followed-up on the incidents in 1995 and ensured that documents and procedures were in place to prevent another spill.

"The specific issue should have been put to bed a long time ago since it first occurred in 1995 by regulators doing their job and ensuring that it was properly addressed," Coon said Wednesday.

"These kinds of incidents with the regulator appearing not to follow through effectively to deal with problems when they're identified undermines confidence in the overall regulation of the operations of nuclear power plants like Point Lepreau."

In 1995, the regulator was the Atomic Energy Control Board. That body was replaced in 2000 by the Canadian Nuclear Safety Commission.

Point Lepreau has been out of service since March 2008 for a major refurbishment that's meant to extend the life of the reactor by 25 years.

The project is three years behind schedule and $1 billion over the original $1.4-billion budget.

It is now scheduled to return to service this fall.